Automated system for improved cooling of aluminum castings in sand molds

ABSTRACT

An improved and efficient method and apparatus for convective cooling of cast sand molds containing molten metal, utilizing vertically-arrayed cooling stations (preferably arranged on a plurality of shelves inside a housing enclosure for temporarily storing said sand molds during their cooling from a molten temperature level to a lower solidification temperature. A draft of cooling air is circulated through said stations in said housing whereby the time for solidifying the molten metal in said cast sand molds is reduced as compared with passive air cooling of said molds. Robot means are provided for moving hot sand molds from a feeding port in said housing to said shelves and for moving cooled sand molds from said shelves to a delivery port in said housing. The robot means is programmed so that the time period of each mold is maintained within said housing according to the individual time required for the solidification of the metal in such individual mold (based on empirical data for typical solidification required for the given individual cast sand mold package or based on other appropriate discernible physical property attributable to achieved solidification).

FIELD OF THE INVENTION

The present invention relates to the field of foundries and metal casting. More particularly, the present invention teaches an improved automated and efficient system for cooling sand mold packages filled with molten metal by air convection cooling minimizing the space necessary for cooling down large numbers of sand mold packages with the additional advantages of improved quality of the castings and savings in capital and in operational costs.

BACKGROUND OF THE INVENTION

In the metal casting industry, molds containing molten metal must be cooled down sufficiently to solidify the metal before passing the casting on to the next steps in the process; such as extracting the casting from the mold and then eliminating the sand cores that were utilized to shape the piece to the desired geometry. In some processes using permanent molds, the cooling of the casting is accelerated by circulating a cooling fluid through certain metallic portions of the mold. The productivity of the foundry is tied to the time needed for the casting to reach the solid state sufficiently so that it can be extracted out of the mold; and then successively filling again said mold for casting the next piece. The time needed for cooling down the casting is longer if the mold is made of sand, since the sand mold package does not have the permanent mold's desirable heat-transfer properties for a rapid cooling, and therefore these sand molds require a longer time for cooling.

The filling of the sand molds with molten metal is done quickly, on the order of about 20 to 50 seconds. Thus, the cooling time is the principal concern. According to long-established practices, it has been necessary to provide a substantial amount of plant space for storing the hot sand packages during their cooling. The sand molds containing molten metal require sufficient spacing for adequate air convection cooling. This practice requires a large footprint area in the foundry and may become a critical factor for increasing the productivity of the foundry.

One of the other drawbacks of the usual current practice concerns liberation of noxious fumes and vapors from the sand molds and their cores caused by the heating of the resins used as binders of the sand molds, which causes odors and contamination of the plant area where the molds and their castings are cooled down.

U.S. Pat. No. 5,771,956 to Kimura only partially addresses the problem in the mass production of castings of a long felt need for more efficient handling during cooling of molds containing molten metal. Kimura describes apparatus having an array of cooling lines comprising several parallel rail lines horizontally arranged to accommodate wheeled mold carriers. This system has the disadvantage of still requiring a large plant space. Furthermore, Kimura is mute regarding the problems and solutions relative to the emission of contaminating fumes and vapors, as well as relative to the need for an increase in productivity by actively reducing the time required for solidifying the molten castings.

This patent is incorporated herein by reference.

OBJECTIVES OF THE INVENTION

The present invention overcomes the disadvantages of the current systems and provides a cooling system for sand molds containing molten metal providing a number of advantages.

It is therefore an object of the present invention to provide an improved cooling system for sand molds containing molten metal which increases the productivity of a foundry.

It is another object of the present invention to provide an improved and efficient cooling system for sand molds containing molten metal which advantageously controls the fumes and odors emitted by the hot sand molds and cores producing a cleaner environment in the foundry.

It is still another object of the invention to provide an improved and efficient cooling system for sand molds containing molten metal which may be operated by automatic programmed robots and equipment.

SUMMARY OF THE INVENTION

The above objects of the invention are generally achieved by providing an apparatus for convective cooling of cast sand molds containing molten metal, comprising: an enclosure housing having a roof and side wall; a plurality of vertically arrayed stations contained inside said housing for temporarily storing said cast sand molds for their cooling from a molten temperature level to a lower solidification temperature level; means for actively producing a draft of cooling air circulating through said stations and around said molds therein from at least one inlet cooling air source in said housing to at least one hot air outlet from said housing whereby the cooling of said cast sand molds is accelerated and the solidification time is reduced as compared with passive air cooling of said cast sand molds; and programmable robot means for moving hot cast sand molds from a feeding port in said housing each to a respective station and for moving cooled cast sand molds containing solidified metal from said respective stations to a delivery port in said housing.

The above objects of the invention are also generally achieved by providing a method for convective cooling of cast sand molds containing molten metal, comprising: feeding cast sand molds containing molten metal into a housing containing a vertical array of closely spaced cooling stations; robotically placing individual cast sand molds each into a respective cooling station; actively circulating cooling air into said housing from at least one cooling air source, through said stations and around said cast sand molds situated therein, and on out of said housing through at least one hot air discharge, whereby the cooling of said cast sand molds is accelerated and the solidification time is reduced as compared with passive air cooling of said cast sand molds; robotically removing individual cast sand molds upon solidification from its respective cooling station; said robotic placement and removal being controlled by applied programming to control the time spent by each cast sand mold within said housing to that needed to achieve solidification of the metal sufficient to permit proper handling in subsequent processing steps; and removing the resulting cast sand molds from said housing.

The present invention advantageously provides an improved and efficient cooling system for sand molds containing molten metal which utilizes vertical space for storing the hot sand molds and thus saves plant area decreasing the capital and operation costs of the casting facility.

The present invention further provides an improved and efficient cooling system for sand molds containing molten metal wherein the sand molds are in contact with a stream of air improving the convection heat transfer and making it uniform through the molds and favorably modifying the cooling process of the castings producing pieces with better quality and mechanical properties avoiding the concentration of residual stresses.

Applicants have found that the apparatus of the present invention not only cools more rapidly, but unexpectedly also results in a decrease in residual stresses in the castings that otherwise may occur due to uneven heat-transfer areas that may develop in the molds, especially for molds with thin walled castings.

It is also a further advantage of the present invention that, not only is space saved in the foundry, but also by confining the forced air convection within an enclosed space, the fumes and vapors produced by the hot resin binder of molds and cores can be controlled and eliminated, providing a cleaner ambient atmosphere in the area.

Furthermore, the applicants have also found that the forced convection cooling of the sand packages improves the overall quality and mechanical properties of the castings by increasing the cooling rate and therefore favorably affecting the solidifying process of the castings.

Other objects and advantages of the invention will be later pointed out, or will be evident to those skilled in the art from the following specification and the attached figures describing some preferred embodiments of said invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side sectional view of a preferred, circular, embodiment of the cooling system according to the present invention.

FIG. 2 is a schematic plan view of the cooling system of FIG. 1.

FIG. 3 is a schematic side sectional view of another preferred, linear, embodiment of the cooling system according to the present invention.

FIG. 4 is a schematic plan view of the cooling system of FIG. 3.

FIG. 5 is a flow chart showing some essential steps of the program controlling the robot for the automatic operation of the cooling system.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS THE PRESENT INVENTION

A preferred embodiment of the invention will be described as applied to the cooling of sand molds containing aluminum alloys for manufacturing automotive motor parts, e.g. cylinder engine blocks and engine cylinder heads.

Referring to FIGS. 1 and 2, there is shown an apparatus for improved cooling of aluminum castings in sand molds comprising a cylindrical housing 10 containing a plurality of vertical shelves 12 which are distributed around at least a portion of the inside of the circular side wall 11 wall of said housing 10 for the purpose of storing sand molds 14 in a cooling environment, while the castings are solidifying. In the illustrated embodiment, each shelf in each unit of the vertical shelving 12 constitutes a single cooling station 15.

The hot newly cast sand molds containing molten metal 14 are introduced through a sand mold inlet port 16 via conveying feed means 18. From there, the robot 20 uses its arm 21 with clamp 23 (shown in dotted outline in FIG. 2) to successively pick up each cast sand mold 14 and, as shown in full outline in the FIG. 2, delivers such mold to a vacant space in said shelves 12 (which space serves as a cooling station 15).

Note that while the position of robotic arm 21 as shown in full outline is the same in both Figures; this arm 21 where shown in dotted outline is depicted differently. In FIG. 1, the robotic arm 21 as shown in dotted outline, in contrast to FIG. 2, is not picking up from port 16, but instead is shown delivering the mold to a differently-located cooling station 15.

Cold air 22 is introduced from a cooling air source inlet 24 by blowing means 26 and circulates within said housing 10 cooling said molds 14 on shelves 12.

Cold air 22 may also be introduced into said housing 10 through a plurality of air inlets 28 positioned at the bottom of the housing side wall 11.

Hot air 30 is withdrawn from said housing 10 by extraction means such as fan(s) 32 operating through one or more air outlets 34 located, for example, at the top of said housing 10. The hot air extraction by means 32 can be sufficient to draw in the cold air through the air inlets 28. Here the means 32 is shown in the form of a plurality of fans.

As an aid in the control and elimination of the fumes and vapors produced by the hot resin binder of molds and cores, which have already been confined within the housing 10 and withdrawn therefrom through the outlets 34, such outlets 34 preferably feed into an optional gas scrubber 35, so that scrubbed air 37 can be vented, thus providing a cleaner ambient atmosphere in the casting foundry area. Robot 20 is programmed to allow sufficient time for each sand mold 14 to cool down and have its contents solidified optimizing the productivity of the cooling system.

The program of robot 20 allows an individualized time allocation for each sand mold 14 according to its heat transfer requirements.

Robot 20 may also be programmed for acting in response not only to a predetermined time period needed for the solidification of the molten metal in a given mold but also may be programmed for acting in response to an intrinsic attribute of the metal present in the mold indicating when said metal is adequately solidified. For example, a suitable temperature sensor may be located in each shelf which may send a signal to the controller of robot 20 triggering the operation of the robot for removing the mold from its shelf and placed on the conveying means 36 for its further processing. Other suitable temperature sensors may be used, for example infrared thermometers mounted on each shelf, or attached to the traveling robot. Also, other properties undergoing changes if sensed or measured when metal passes from the molten state to solid state may be utilized for automating the cooling system operation and therefore increasing its productivity.

The vertical arrangement of shelves 12 permits handling and cooling of more sand molds 14 in a smaller footprint, decreasing the capital costs for production expansions in foundries.

This invention keeps sand molds 14 static during the whole cooling process reducing capital and operation costs as compared with the cooling systems that are based on conveyors, as for example described in Kimura.

After solidification of the metal, robot 20 removes the cooled sand molds 14 from shelves 12 and places them on a conveying discharge means 36 which takes the cooled sand molds 14 through a sand mold outlet 38 for further processing. In another embodiment of the invention a single conveying means passing across said housing 10 may be used both for introducing and withdrawing sand molds 14.

Referring now to FIGS. 3 and 4 where same numerals designate equivalent elements shown in FIGS. 1 and 2, enclosure housing 10 has a rectangular shape and a plurality of shelves 12 are vertically arranged in a linear lay-out. Robot 20 is programmed to move sand molds containing molten metal 14 from conveying means 18 to a vacant space in said shelves 12. After cooling and solidification of the metal, robot 20 removes the cooled sand molds 14 from shelves 12 and places them on conveying means 36 which takes the molds out of the housing 10 for further processing. Robot 20 travels alongside shelves 12 by rolling over rails 25 in a manner known in the art and can move sand molds 14 to and from shelves 12, one in front of the other. Robot 20 may also travel suspended from overhead rails (not shown) instead of rolling or sliding over ground-level rails, and may serve more than two cooling stations arranged in a variety of geometrical arrangements as may best fit a particular plant lay-out.

Referring to FIG. 5, robot 20 may follow the sequential steps shown in the diagram for automating the operation of the cooling system from the moment the sand molds 14 are picked by robot 20 from inlet conveyor 18 up to the moment when the robot 20 removes the cooled sand mold 14 from its shelf 12 and places it on outlet conveyor 36.

According to one of the preferred embodiments of the invention, robot 20 identifies the sand mold 14 with molten metal at inlet conveyor 18 and identifies a vacant shelf 12 for storing said mold 14. Robot 20 sets the initial values of cooling time or solidification indicator and reads actual values of cooling time or other solidification indicator of a mold 14 and determines whether said value has reached a predetermined setting.

Robot 20 then removes sand mold 14 from its shelf 12 and places it on outlet conveyor 36. Robot 20 identifies the now empty shelf as being vacant and repeats the program.

It is of course to be understood that the above specification is illustrative only and that the described embodiments are given for illustration and not for limitation, and that numerous modifications may be made to these embodiments without departing from the scope and spirit of the invention, which is limited only by the scope of the following claims.

For example, the cylindrical housing 10 as illustrated in FIG. 2 could be larger; so that shelving 12 could be ranged along the inner side of the side wall 11 of housing 10 on both sides of the conveying means 18 & 36 (which means 18 & 36 in turn are aligned with a diameter of housing 10, and with robot means 20 being positioned between the ends of said conveying means 18 & 36). Also, the shape of the housing 10 need not be strictly cylindrical or linear and may instead take any form that best suits the robot means 20, including among other possibilities, a non-linear layout where the robot 20 may travel alongside the shelves and between the sand mold inlet 16 and sand mold outlet 38. Other variations may involve the number of air blowing 26 and air extracting 32 means used. These may be selected in number, orientation, and capacity according to the specific design of any particular application of this invention (including choosing one to the exclusion of the other). 

1. An apparatus for convective cooling of cast sand molds containing molten metal, comprising: an enclosure housing having a roof and side wall; a plurality of vertically arrayed stations contained inside said housing for temporarily storing said cast sand molds for their cooling from a molten temperature level to a lower solidification temperature level; means for actively producing a draft of cooling air circulating through said stations and around said molds therein from at least one inlet cooling air source in said housing to at least one hot air outlet from said housing whereby the cooling of said cast sand molds is accelerated and the solidification time is reduced as compared with passive air cooling of said cast sand molds; and programmable robot means for moving hot cast sand molds from a feeding port in said housing each to a respective station and for moving cooled cast sand molds containing solidified metal from said respective stations to a delivery port in said housing.
 2. An apparatus according to claim 1, wherein said robot means is programmable for introducing and then for withdrawing said molds after a given time interval as required for the solidification of said metal therein.
 3. An apparatus according to claim 2, further comprising conveying means for introducing said cast molds containing molten metal into said housing.
 4. An apparatus according to claim 3, further comprising conveying means for withdrawing cooled molds containing adequately solidified metal from said housing.
 5. An apparatus according to claim 4, wherein there is a single inlet for said cooling air source which is located at a central part in the roof of said housing.
 6. An apparatus according to claim 5, wherein said means for actively producing a draft of cooling air is a blowing means in said single inlet located above said stations.
 7. An apparatus according to claim 6, wherein there are a plurality of hot air outlets located spaced at the outer periphery of the roof of said housing.
 8. An apparatus according to claim 7, wherein there are a plurality of inlets for said cooling air source located at the lower part of said housing.
 9. An apparatus according to claim 8, wherein said means for actively producing a draft of cooling air includes extraction means in the form of fans each in a plurality of hot air outlets located spaced at the outer periphery of the roof of said housing and above said stations.
 10. An apparatus according to claim 9, wherein said extraction means is structured to withdraw hot air through the roof of said housing.
 11. An apparatus according to claim 1, wherein said vertically arrayed stations are shelves disposed in a linear arrangement and said robot means travel alongside said shelves.
 12. An apparatus according to claim 1, where said housing has a cylindrical shape; and said robot means is located anchored in the center of said housing, and said vertically arrayed stations are a single set of shelving circularly arranged around said robot means.
 13. An apparatus according to claim 12, where said vertically arrayed stations are a single set of shelving arranged in a semi-circle around said robot means.
 14. An apparatus according to claim 13, further comprising scrubbing means for cleaning any noxious gases emanating from said cast sand molding within said housing.
 15. A method for convective cooling of cast sand molds containing molten metal, comprising: feeding cast sand molds containing molten metal into a housing containing a vertical array of closely spaced cooling stations; robotically placing individual cast sand molds each into a respective cooling station; actively circulating cooling air into said housing from at least one cooling air source, through said stations and around said cast sand molds situated therein, and on out of said housing through at least one hot air discharge, whereby the cooling of said cast sand molds is accelerated and the solidification time is reduced as compared with passive air cooling of said cast sand molds; robotically removing individual cast sand molds upon solidification from its respective cooling station; said robotic placement and removal being controlled by applied programming to control the time spent by each cast sand mold within said housing to that needed to achieve solidification of the metal sufficient to permit proper handling in subsequent processing steps; removing the resulting cast sand molds from said housing.
 16. The method of claim 15, wherein the cast sand molds containing molten metal are all essentially the same and the robotic programming retains each such mold in its cooling station in the housing for a time determined to be minimally required for adequate solidification of the molten metal and is thereafter promptly removed from the housing.
 17. The method of claim 15, further comprising monitoring in each cooling station any cast sand mold present therein to sense the presence of an intrinsic attribute of the metal present only when adequately solidified and promptly removing such mold from the station and the housing upon sensing such an intrinsic attribute, irrespective of when such mold was introduced into the housing relative to when the other molds within the housing.
 18. The method of claim 17, wherein the intrinsic attribute is a given surface temperature of the mold, which temperature has been determined to be indicative of adequate solidification of the metal within the cast mold.
 19. The method of claim 15, further comprising cleaning any noxious gases emanating from any cast sand moldings within said housing.
 20. The method of claim 18, further comprising cleaning any noxious gases emanating from any cast sand moldings within said housing. 